Not necessarily. I don’t think there are any laws against it, unless you are doing it on purpose and combining it with other offensive behavior that is chargeable.
Whether they charge you for something else because you farted I expect depends on the officers, their imagination and mood, your other behavior and chargeworthiness. I think in general it probably wouldn’t make them like you more, so that might incline them to charge you, especially if they have other reasons to dislike you. If they don’t dislike you and were on the fence about charging you and it’s not too late for them to back out, I suppose they might take it as a reason to cut you loose.